As is generally known in the art, a hydraulic breaker includes a head cap having hydraulic passages for supplying and receiving hydraulic pressure, a cylinder having a cylinder chamber, in which a piston is reciprocated, and elements, e.g. valves or the like, for operating the piston, and a front head having a striking rod, which is connected to the piston so as to implement a striking stroke through reciprocating operation. The above constitutional elements are separately formed and are combined into a single unit by four long bolts. In operation, the piston strikes the rod while moving up and down by means of hydraulic pressure supplied to the cylinder, so that the rod can break a rock or the like.
As shown in FIG. 1, a conventional hydraulic breaker 10 in the related art includes a cylinder 50 having a piston therein, a front head 40 installed on a lower end of the cylinder 50 and having a rod 70 therein as striking means, and a head cap 30 connected to an upper end of the cylinder 50, wherein the head cap 30, the cylinder 50, and the front head 40 each have through-holes, into which long bolts 80 are inserted so as to connect them.
Herein, nuts fastening the long bolts 80 are coupled to the bolts in mounting holes 40-2 provided in the front head 40, and the side faces of the front head, the cylinder, and the head cap are supported by variable dampers 30-1, 30-2, 40-1, and 50-1 inserted into the inside of the casing 60.
In the breaker 10, when a hydraulic or pneumatic pressure source is supplied to the inside of the cylinder 50, the piston moves down to strike the rod 70 provided in the front head 40, so that the rod 70 in turn strikes and breaks an object.
However, such a breaker has a problem in that, when distortion stress occurs in the striking rod upon striking rocks or the like, the distortion stress is concentrated on connecting portions between the front head and the cylinder and between the cylinder and the head cap, so that the stress is applied to the long bolts threaded through the connecting portions, causing deformation such as bending or breakage, thereby deteriorating the reliability of the connection.
Further, another problem is that the construction of the plurality of variable dampers 30-1, 30-2, 40-1, and 50-1, which are provided on the inside of the casing 60 so as to support the front head 40, the cylinder 50, and the head cap 30, respectively, suffers from abrasion resulting from friction caused by vibrations or the like, which increases the shear load applied to the long bolts 80, thereby degrading the durability thereof.
In order to solve this problem of abrasion in the variable dampers, Korean Registered Utility Model No. 381252 has been disclosed, which, as shown in FIG. 2, includes a bracket assembly having front and rear brackets 3a and 3b and a plurality of side brackets 3c, which are assembled into a box shape to form an assembling space into which an assembly body is inserted, and a bulk member 4 and a lower member 5 respectively assembled on upper and lower portions of the bracket assembly with upper and lower dampers 7a and 7b composed of urethane interposed therebetween, wherein the assembly body has a piston which moves up and down when pressure is applied thereto, and a chisel 6 receiving an impact force from the piston.
In the assembly body, a plurality of side dampers 8a, 8b, and 9a is disposed, the side dampers 8a and 8b consisting of respective urethane members 81a and 81b and pairs of front and rear plates 83a and 82a and 83b and 82b, which are disposed on opposite sides of the urethane members so as to be assembled with assembling protrusions 31 provided in the front and rear brackets 3a and 3b, and being composed of wear-resistant synthetic resinous material.
However, such a hydraulic breaker has problems as follows. Since the urethane members become damaged due to frequent vibrations and impacts, gaps are created between the assembly body and the side dampers, generating noise and vibrations. Since the piston cannot accurately strike the chisel as the gaps expand gradually, the damage to the assembly body is accelerated, and the durability and reliability of a product are reduced. Since all the side dampers have to be replaced when eccentric abrasion occurs, unnecessary waste is caused.